This invention relates to an electromagnetic pump, and more particularly to an electromagnetic pump adapted to convey molten metal.
A conventional electromagnetic pump generally comprises an outer conduit made of heat resistant material, for example ceramics, and with one end communicated with the interior of a vessel containing molten metal, an inner conduit with the inner end closed and concentrically disposed within the outer conduit for defining a passage for the molten metal, an induction or exciting coil wound about the outer conduit, and a coupling surrounded by a reinforcing ring made of iron and connected to the outer end of the outer conduit, the coupling being connected with a vertical conduit for supplying the molten metal to a casting machine, for example.
For the purpose of preventing temperature decrease of the molten metal while it flows through the magnetic pump and the vertical conduit, according to a prior art construction, at least one cartridge electric heater is inserted vertically through the iron ring. With this construction, however, as the cartridge electric heater is provided for the massive iron ring it takes a long time for reaching a desired high temperature. Moreover, as the heat dissipating area of the iron ring is large it is necessary to increase the rating of the cartridge heater.
According to another prior art electromagnetic pump, an electric heating wire is helically wound about the outer surface of the outer conduit and the exciting coil is disposed about the electric heating wire via a heat insulating cylinder. With this construction, it takes a long time and much labor to disassemble electromagnetic pump, remove the broken heating wire, mount a new heater and reassemble the electromagnetic pump. During this repair, the operation of the casting machine must be stopped, thus reducing productivity. Furthermore, it is necessary to use a thick insulating cylinder for preventing heat from being transmitted to the exciting coil.
According to another type of the electromagnetic pump, a hollow inner conduit containing a magnetic core is secured to the side wall of the vessel containing molten metal through a clamping plate which is bolted to the side wall of the vessel with nuts threaded to the bolts with compression springs interposed between the nuts and the clamping plate. With this construction, for exchanging the magnetic core, the clamping plate is removed whereby both inner and outer conduits are loosened so that care must be taken for reassembling the electromagnetic pump to prevent leakage of the molten metal.